Since the discovery of hydrothermal vents in 1977, research in chemosynthetic environments has provided many surprises about life in the deep-sea. One of the most startling discoveries in recent marine biology was the diverse and specialized fauna found at large organic falls such sunken whale carcasses. To date more than 400 species have been found associated with these habitats, 30 of which are presumably endemic. The sulphide and lipid-rich nature of decomposing whalebones is thought to create an habitat intermediate to that of vents and seeps, and have allowed several vent/whale conspecifics to use large organic falls as dispersal stepping-stones over evolutionary or ecological time-scales. In the last 10 years detailed ecological phylogenetic studies have been carried on large organic falls and several in situ experiments have been set. Surprisingly, all published studies have been restricted to the Pacific Ocean. With this project we propose to study the deep-sea community response to intense pulses of organic falls and their importance as sulphide-rich habitat islands at the Atlantic Ocean deep-sea floor. For this purpose two mammal carcasses will be deployed in two sites where cetaceans naturally occur, the Setubal canyon and the Sao Jorge Channel. These two in situ experiments will allow comparing the colonization dynamics and species composition between areas with different geological and hydrological settings and address questions related to species distribution, dispersal strategies and phylogeography. Each of the experimental sites will be surveyed and sampled every six months during two years allowing the identification of succession patterns on species turnover and trophic structure. There are two main constraints in the study of deep-sea organic falls: 1) the access to advance manned or unmanned submersibles and 2) the need of regular sampling because of the significant changes in faunal composition during community succession. These limitations will be addressed first with the use of the deep-water ROV Luso recently acquired by the Portuguese Ministry of National Defense and made available to the scientific community, and second by a careful choice of the experimental sites, which due to their proximity to shore will allow an efficient use of ship-time. The project is organised in five tasks that aim at the accomplishment of five main objectives: 1) to describe deep-water mammal carcasses fauna in the Atlantic, 2) to investigate functional anatomy of organic-fall specialists, including potential bacterial endosymbioses, 3) to determine phylogenetic relationships of organic-fall specialists and their closest relatives to evaluate evolutionary hypotheses 4) to analyse the trophic structure of colonizing metazoan assemblages 5) to elucidate the importance of large organic falls as a stepping-stone habitat for vent and seep species in the Atlantic. A sixth task will aim at public outreach and education by making the scientific knowledge acquired during this study available to the general public and stakeholders such as NGO’s and policy makers. The project joins two main national research institutions in marine sciences and a total of 9 members with a strong expertise in the study of deep-sea chemosynthetic ecosystems, from taxonomy and anatomy of invertebrates, to trophic and reproductive ecology and biogeography.

CESAM members on this project

Ana Hilário
Principal investigator

Ana Raquel Marçal
Researcher

Clara F. Rodrigues
Researcher

Luciana Génio
Researcher

Researcher

Newton Carlos Marcial Gomes
Researcher